This application claims the priority of German application 197 08 936.4 filed in Germany on Mar. 5, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a yarn traversing device on textile machines producing cross-wound packages, comprising at least one traversing rod extending in machine longitudinal direction over a plurality of winding stations and subjected alternately to tension and compression. The traversing rod is driven at one end by means of a traversing drive, and at a distance therefrom, preferably at its other end, can be driven by at least one auxiliary traversing device for accelerating its return of motion, which auxiliary traversing device can be activated for short intervals by a control mechanism.
Traversing rods are alternately accelerated by the traversing gear. The highest tension and compression load occurs with each reversal of motion direction. In particular in the case of long machines, there are considerable delays in the reversal of motion at the machine end facing away from the traversing gear. The mass accelerated in one direction hinders delay-free return of motion. This inertia must be overcome. With one reversal of motion, a considerable elongation of the traversing rods occurs and with the other reversal of motion a corresponding compression of the traversing rods occurs. Length changes in the traversing rods measuring several millimeters occur. In the case of a long machine it is to be feared that the lifting motion is increased in both directions at the machine end, caused on the one hand by elongation and on the other by compression, which results in the dimensions of the packages varying. The yarn guides located on the traversing rods do not undergo their return of motion exactly where they should.
In order to reduce the tension swings during the reversal of motion of such traversing rods, German published patent application 38 10 734 A1 teaches that the traversing rods are connected in the area of their ends to pneumatic energy storers. Towards the end of the motion in a direction of the traversing rod, the air is compressed in a piston-cylinder unit, by means of which a corresponding counterforce is exerted on the traversing rod at the moment of return motion. During the motion towards the piston-cylinder unit, the energy storer is charged, and the stored force effects the acceleration of the return motion.
The known energy storers are designed so that during operation a tension is exerted on the traversing rods, regardless of their direction of motion. The compression forces shall thus be compensated. For this purpose, a blast of compressed air is exerted on a piston connected to the traversing rod, when the traversing rod changes from a tension movement to a compressed movement. This additional compressed air is only effective in one direction of motion. The change in length of the traversing rod is not hereby compensated, but rather its pressure load is. A lighter construction of the traversing rod is thus desirable.
It has also been ascertained that during operation of long textile machines which produce cross-wound packages, the machines are never equally long over a longer period time. The climate plays a role here, as well as heat expansion and other occurrences such as the "strain" of the machine, as it is known in the industry. This strain of the machine applies not only to its height but also to its length. This point is not discussed in German published patent application DE 38 10 734 A1, and due to the additional blast of compressed air which is only effective on one side, this cannot be counteracted.
It should be considered that the "auxiliary traversing device", activated by the additional blast of compressed air, is only then purposeful when it is effective exactly at the same time, to the very millisecond, as the return motion. If the walls of the cylinder and piston alter their distance with respect to one another even slightly as a result of changes in length, than the effect of the auxiliary traversing device is already questionable. If the auxiliary traversing device is effective at the wrong time, it can, in extreme cases, do more harm than good.
It is thus an object of the present invention to take into account the changes in length, caused by the expansion and compression of the long traversing rods, and to generate packages with almost identical dimensions even on those winding stations which are further away from the traversing gear.
This object has been achieved in accordance with the present invention in that the auxiliary traversing device can be activated in both directions of the traversing rod by a synchronous signal given by a traversing gear.
Due to the auxiliary traversing device being activated in both directions of motion, the change in length of the traversing rod during tensile load and during compression are accommodated equally.
The command to activate the auxiliary traversing device at the machine end is given by a non-mechanical means. The signal transmitter for the traversing rod, be it direct or indirect, is the traversing gear itself. In close proximity to the traversing gear there is hardly any falsification which could result in unwanted changes in length of the traversing rod. The return motion in both directions takes place synchronous with the signal from the traversing gear.
In order that elongations are prevented, which can otherwise measure up to 4 to 5 mm, a timely counterforce is effected at the machine end, namely not when the traversing rod reaches the auxiliary traversing device, but when the traversing gear has initiated the return motion. Thus unacceptable elongations and compressions of the traversing rod are at least so far avoided that changes in the lengths of the packages remain within tolerable limits. The auxiliary traversing device is designed so that its exact adjustment in longitudinal direction in relation to the traversing rod is not of great importance. At the moment of desired return motion, clocked by the traversing gear, a counterforce is released, which prevents elongation as well as unacceptable compression.
Traversing gears comprise, as a rule, a cam drum, for example a grooved drum or a beaded drum. Their movements are transmitted directly or indirectly to the traversing rod. In one embodiment of the present invention it is thus provided that the traversing gear comprises a cam drum, and that the cam drum, or a similar component located in close proximity and driven synchronous to the cam drum, contains at least one signal transmitter for the auxiliary traversing device.
Each angle position of this cam drum corresponds to an exactly determined position of the yarn guides located at each winding station, which yarn guides are arranged on the traversing rod. These positions are chonologically and spatially exactly set with respect to their reversal of motion. It is known in which position the cam drum initiates the reverse motion, that is, at which point in time the change from tension to compression and the reverse, takes place. The actual activating of the auxiliary traversing device takes place in a clearly ascertainable and always constant angle position of the cam drum.
The command does not have to come from the cam drum itself. However, the signal transmitter should be arranged at a component which exactly conforms in its movement with the cam drum. The traversing rod itself could be used for transmitting the signal, so long as this occurs at a point which is adjacent to the traversing gear. In this area, practically no unacceptable changes in length occur.
At least one signal receiver is arranged spatially with respect to the signal transmitter, which signal receiver is connected electrically with an initiator of the auxiliary traversing device. When, for example, the cam drum reaches a certain position, the signal receiver receives a signal from the signal transmitter arranged at the cam drum, which signal is electrically relayed to the other machine end. The auxiliary traversing device is thus activated at exactly the right moment.
It can be advantageous when the signal given by the signal transmitter is slightly ahead of the impulse transmitted from the initiator to the auxiliary traversing device. The signal thus arrives slightly prematurely, for example to accommodate delays during opening or closing of a valve. The opening times of such valves are known to be the same over a longer period of time, so that an advance is possible without any negative effects on an exact timing. In this connection it should be mentioned that today there are valves which regulate their own opening and closing times and which transmit any changes registered to a small computer which processes these changes and effects a corresponding adjustment of the initiators.
It is not absolutely necessary to arrange the auxiliary traversing device at the end of the traversing rod. Rather, embodiments are contemplated wherein a plurality of auxiliary traversing devices are provided along the traversing rod. All these auxiliary traversing devices would have the same purpose, namely to speed up and facilitate the return of the traversing movement, and to prevent unacceptable elongations or compressions of the traversing rods occurring. If, for example, an auxiliary traversing device were located at each machine section, then the traverse motion would function ideally. This is, however, a question of cost.
An energy storer, charged by the traversing rod itself, may be arranged at the auxiliary traversing device. The energy storer is charged shortly before the return motion points by means of the kinetic energy and becomes effective, as in prior art mentioned above. For example, a pressure spring can be provided at each section, which pressure spring is compressed towards the end of the lifting movement, and which then gives back the input energy at the moment of return motion. Even if this additional energy storer is not controlled by the traversing gear, the controlled auxiliary traversing device can be effectively supported thereby and can, as required, be executed in a less powerful form.
Advantageously the auxiliary traversing device comprises a pneumatic piston-cylinder unit, which is controlled by the traversing gear and releases a blast of compressed air at the right moment. It is hereby important that the main blast occurs exactly, to the millisecond, at the right moment.
Alternatively, other auxiliary traversing devices are also contemplated. For example, it would be possible at each machine section to insert the traversing rod through an electromagnetic spool. The electromagnets would be connected electrically with the traversing gear, so that they would become effective at the correct time.
If the yarn guides at the winding stations were always controlled to execute their return motion at the same place, poor package edges may be the result. Experience has shown that the edges of the packages improve when they are periodically moved back and forth by small amounts. This is achieved as a rule in that the cam drum is driven periodically to execute small traversing movements. According to the present invention, the signal transmitters and the signal receivers are adapted to the small traversing movements, which involve small distances of up to a maximum of +/-4 mm. If, for example, a pneumatic auxiliary traversing device is used, the additional traversing motion of the cam drum need not be taken into account. The pneumatic cylinders are continually blasted with compressed air when the actual return motion is to take place, independent of the current position of the piston which is connected with the traversing rod. What is essential is that the commands for the return of the direction of motion are given at the correct time.